UNIT 4 BI SL

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Define natural selection and fitness

- survival of the fittest

- an organism's ability to pass its genetic material to its offspring

Outline the process of natural selection and the resulting evolution of the population.

Individuals with adaptive traits—traits that give them some advantage—are more likely to survive and reproduce. These individuals then pass the adaptive traits on to their offspring. Over time, these advantageous traits become more common in the population.

Compare the reproductive success of better and less well-adapted individuals in a population.

Better adapted individuals survive and are able to reproduce to pass on the adapted characteristic to their offspring. Less adapted individuals have a lower reproductive rate as most are less likely to survive.

State how the biodiversity of life came to be.

Natural selection has operated continuously over billions of years, resulting in the biodiversity of life

Explain why Darwin's evidence of evolution via natural selection resulted in a paradigm shift in the understanding of how life evolves.​

before darwin's theory, the belief was that evolution happens because an organism passes on any traits that they acquire during their lifetime, according to lamarckian evolution

Define biological variation.

The genetic differences between organisms within a population

Explain why natural selection can only function if there is variation in a species.

Variation in living things exists as a consequence of mutation. A mutation is a change in the base sequence of a DNA molecule.
When this happens, a new allele (variety of a gene) is formed.

Compared to the original allele, the new allele might offer:
1. A survival advantage
2. A survival disadvantage
3. No effect on survival

Outline sources of genetic variation (mutation, meiosis and sexual reproduction).

- mutation (which can create entirely new alleles in a population),
- random mating,
- random fertilization,
- recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

Compare variation that results from mutation to those that is generated from sexual reproduction

In addition to the formation of new alleles by mutation, sexual reproduction leads to new combinations of alleles.
There are two main random events in sexual reproduction that increase variation:
1. Production of gametes-when sperm and eggs are produced, it is random which copy of each gene is passed on.
2. Random fertilization-there is some randomness in which sperm fertilizes which egg.

State whether species have the ability to produce more offspring than the environment can support or not.

species have the ability to produce more offspring than the environment can support to increase the chances of the survival of offspring.

Use an example to illustrate the potential for overproduction of offspring in a population.

frogs lay an obscenely large amount of eggs to increase the probability that the line continues.

Describe competition for resources as a consequence of overproduction of offspring

1. All species overproduce offspring.
2. Resources (food, space) are finite.

Therefore, there is competition to survive.

3. Individuals in a species show variation.
4. Some variations are more likely to survive.
5. The individuals that survive pass on their genes.

Therefore, the most beneficial variations will be more common in the next generation. This applies every generation, so evolution is continuous and has been over the billions of years of life on Earth.

Define selective pressure.

environmental factors that affect the survival (or reproductive) chances of an organism

Compare density-independent and density-dependent selective pressures

Density-dependent factors (usually biotic):
- Predation pressure,
- food,
- diseases

State example abiotic selective pressures.

- Temperature,
- pH,
- salinity,
- light availability,
- water

Outline how a selective pressure acts on the variation in a population.​

low temperatures require adaptations to conserve heat as effectively as possible.

The polar bear's adaptations to conserve heat include:
- Thick layer of blubber for insulation
- Specialized fur that reflects body heat back inward more effectively than other mammals
- Black skin absorbs this reflected radiation effectively
- Small ears to prevent heat loss and avoid frostbite

Define adaptation and fitness.

- the evolutionary process whereby an organism becomes better able to live in its habitat or habitats
- an organism's ability to pass its genetic material to its offspring

Explain the effect of the selective pressure on the more and less adapted individuals in a population. ​

Gradually, the population changes, and genes that improve survival and reproduction will become more common, while genes that are disadvantageous to survival and reproduction will become more rare.

Explain adaptation as a consequence of intraspecific competition.

The major impact of intraspecific competition is reduced population growth rates as population density increases. This means that only those with the most advantageous traits in the species will be able to survive, reproduce and evolve.

Explain why only heritable characteristics can be acted upon by natural selection.

Because alleles are passed from parent to offspring, those that confer beneficial traits or behaviors may be selected, while subtly harmful alleles may not.

Outline the mechanism of sexual selection in evolution of courtship behavior and anatomical features.

In some species, however, there are traits that seem to decrease the chances of survival.
For example, the large, showy tail of the peacock is large, heavy, and highly visible.
While the peacock's tail negatively affects survival chances, it provides the peacock with a much better chance of attracting a peahen to mate with, so the trait has become more common anyway.
This type of selection is called sexual selection.

Summarize John Endler's experiments with guppies which demonstrate selection for and against coloration in different habitats.

Low coloration makes them less visible to predators.
High coloration allows them to be more attractive (sign of health)

Outline the selective pressures for and against coloration in guppies.

With high predator pressure, male guppies tend to have less colorful patterns, (less visible to predators).
When predators are less common or absent, it is likely to be better to be bright.

Define evolution.

the change in the heritable characteristics of a population over time.

Distinguish between heritable and acquired characteristics.​

Heritable characteristics are the characteristics encoded in the DNA. This serves as a contrast to acquired characteristics, which accumulate over an organism's life.

what is considered to be evidence of evolution?

similarities and differences between DNA, RNA and amino acids sequences can be evidence for evolution.

Discuss sequence data showing evidence for evolution within a species.

DNA sequencing graphs show the similarity of humans to a variety of different species. It has also led us to revise some classifications, but on the whole it confirms common ancestry.

Outline the relationship between time, evolutionary relationships and biological sequence (nitrogenous base or amino acid) similarities between species.

It is not always obvious which species have evolved from a common ancestor and should therefore be included in a clade.

If possible scientists will use the base sequences of genes or the amino acid sequences of proteins.

The more similar the sequence, the less time has past for the sequence to acquire mutations and diverge from each other so the more recent the common ancestor, the more closely related the organisms.

Sometimes amino acids sequences don't provide enough detail, so DNA or RNA base sequences are used to compere closely related organisms.

Define selective breeding and artificial selection.

a process by which humans are able to guide the evolution of a species by selecting which individuals will breed and which will not

List reasons why humans have selectively bred domesticated animals and crop plants.

- more rapid development
- control over the outcome
- produce bigger yields

Outline how selective breeding can lead to rapid evolutionary change.

over time, the species' performance can drastically improve as specific traits are emphasized and passed down through generations.

Explain an example of artificial selection in a crop plant.

Corn was produced by indigenous peoples of Mexico through selective breeding of teosinte.

Farmers noticed that some teosinte plants had more and/or larger kernels than others.

By planting seeds from plants that produced the most kernels, over time the number of kernels per ear was increased.

Explain an example of artificial selection in a domestic animal.

To make a dog breed run faster, they get a sample of dogs, select the fastest males and fastest females, and have them breed puppies, then repeat steps 1 and 2 with the puppies multiple times.

List examples of different types of homologous structures at different levels of biological organization.

- A dolphins flipper,
- a cats leg,
- a birds wing,
- a human arm

Define pentadactyl limb.

A limb with five fingers, found in amphibians, reptiles, birds and mammals.

List the bone structures present in the pentadactyl limb (specific names of bones are not required).

- the upper arm or thigh containing one long bone, (humerus/femur)
- the forearm or shank containing two long bones, (radius and ulna/tibia and fibula)
- and the hand or foot, which contains a number of small bones. (carpals and metacarpals/tarsals and metatarsals..., and phalanges)

Identify pentadactyl limb structures in diagrams of amphibians, reptiles, birds and mammals

Relate differences in pentadactyl limb structures to differences in limb function.

Hind limbs in monkeys help them climb trees and jump, while hind limbs in pigs help them walk or run around in any terrain.

Define divergent evolution.

when species sharing a common ancestry diverge from each other over time due to differential selection pressure.

Describe how divergent evolution explains the pattern found in pentadactyl limb structure yet allows for the specialisation of different limb functions.​

divergent evolution forms homologous structures as is in the case of pentadactyl limb structures, which show functional diversity but similar anatomical features indicating a shared common ancestor resulting from divergent evolution.

State an example of an analogous structure found in two species.

the common ancestor of the bat and the dragonfly did not have wings, but both have since evolved wings.

Outline how convergent evolution results in analogous structures.​

when two groups of largely unrelated organisms are exposed to very similar environments and develop similar adaptations to survive.

Define speciation.

when new species arise on Earth by the splitting of pre-existing species.

Compare the process of speciation with that of gradual evolutionary change in an existing species.

Scale of Change:
--Gradual Evolutionary Change: Usually pertains to phenotype modifications, such as color variations or slight morphological changes.
--Speciation: Entails foundational genetic shifts that beget entirely new species.

Reproductive Considerations:
--Gradual Evolutionary Change: Despite variations, populations can interbreed successfully.
--Speciation: Genetic differences obstruct successful interbreeding.

Timeframe:
--Gradual Evolutionary Change: Might manifest over shorter evolutionary timescales.
--Speciation: Generally unfolds over extended periods, especially if driven solely by natural selection without geographic barriers.

State the impact of speciation and extinction on the total number of species on Earth.

Each speciation event increases the number of species that exist on Earth.
Each extinction event lowers the number of species that exist on Earth.

List two processes required for speciation to occur.

-allopatric speciation
-sympatric speciation

Define reproductive isolation.

when new species similarly appear when populations are split and can no longer interbreed

Outline how reproductive isolation and differential survival lead to speciation.

Speciation involves reproductive isolation of groups within the original population and accumulation of genetic differences between the two groups. In allopatric speciation, groups become reproductively isolated and diverge due to a geographical barrier.

Outline the speciation between chimpanzees and bonobos.

The speciation of the chimp and bonobo was driven by the formation of the Congo River around 1.5-2 mya. Chimpanzees avoid water altogether, and bonobos never enter water more than waist-deep.
Since the Congo River is the deepest river in the world, it is an effective barrier for these two species, and reproductive isolation resulted.

Define organism.

any biological system that functions as an individual life form. all organisms are composed of cells.

Define variation.

differences between members of a group (between same species and different species)

List sources of genetic variation within a species.

- mutation
- genetic recombination
- gene flow

Compare discrete and continuous variation. ​

discrete variation:
- traits that can be put into distinct qualitative categories.
- usually influenced by one or a few genes
- can be influenced by the environment (usually not significantly)

continuous variation:
- trait that vary along a quantitative continuum (most types of variations are continuous)
- results from complex interactions between many different genes (polygenic)
- phenotype expression is influenced by the environment (significantly)

Compare variation within and between species.

intraspecies variation: variation within a species
- inheritable
- results from: mutation, gene flow, meiosis
- enable populations to survive better

interspecies variation: variation between species
- amount of variation depends on how closely related they are
- have more variation than the variation between individuals of the same species
- species from different domains have the most variation

Define species according to the morphological species concept.

groups of individuals that are morphologically similar to one another and are morphologically distinct from other such groups.

Define binomial nomenclature.

the system of nomenclature where two terms are used to name a species, the first indicating the genus and the second the species.

State four rules of binomial nomenclature formatting.

1. The binomial name is always italicized
2. the first word (genus) capitalized
3. the second word in lowercase
4. It is also accepted to abbreviate the genus once the full name has been used once (example: E. coli, T. rex)

Outline why the binomial naming system is used in science rather than local names.

it gives the species a universal name, understood by everyone.

Define species according to the biological species concept.

Under this concept, a species is a group of organisms that can interbreed and produce fertile offspring.

Describe limitations of the biological species concept, with mention of hybrids and geographical separation. ​

-can only be applied to sexually reproducing species. (asexually reproducing species don't interbreed, the biological species concept can never apply to them)
- can't be applied to extinct species, (no way to gather data on their reproductive compatibility)
- leads to some conclusions that seem wrong. (ie: closely related species are capable of producing fertile hybrids, lion x tiger or polar bear x grizzly bear.
The morphological species concept and popular thought distinguish these species, but the biological species concept suggests that lions and tigers are one species.)

Define speciation.

the process by which one species splits into two or more species

Explain the difficulties in distinguishing between populations and species during speciation. ​

Evolutionary changes happen gradually -- for long periods of time, two populations may be in the process of splitting into two species, but it's impossible to say precisely when speciation is complete. This gradual divergence makes it challenging to apply the biological species concept when there are two closely-related neighboring populations.
If we observe that two populations don't interbreed, is that sufficient to conclude that they can't interbreed?
Laboratory experiments in hybridization could be carried out, but they raise ethical questions and have little value beyond answering the question of reproductive compatibility.

State a distinguishing characteristic of a species.

chromosome number

Explain why the typical number of chromosomes in a diploid cell is an even number.

Diploid cells always have an even number of chromosomes because there are two copies of each chromosome, one contributed by the male sperm and one by the female egg.

State the number of chromosomes in humans and in chimpanzees. ​

Human = 46 chromosomes
chimpanzee/gorilla/orangutan = 48 chromosomes

Evaluate the evidence for the hypothesis that chromosome 2 in humans arose from the fusion of chromosomes 12 and 13 with a shared primate ancestor.

It turns out that chromosome 2, which is unique to the human lineage of evolution, emerged as a result of the head-to-head fusion of two ancestral chromosomes that remain separate in other primates.

Define karyotype and karyogram.

karyotype: the number of chromosomes in a eukaryotic nucleus
karyogram: image that shows karyotype

List the characteristics by which chromosomes are paired and arranged on the karyogram.

• Homologous pairs are arranged together with matching length, centromere position, and banding pattern (The banding patterns show from using chemical stain. The darkness of the stain depends on the relative proportion of A-T vs C-G pairs there are in different regions of the chromosome.
  This allows homologous chromosomes to be identified more easily)

• They are ordered from largest to smallest.

Define autosome and sex chromosome.

Autosome: any chromosome that is not a sex chromosome

Sex chromosome: type of chromosome responsible for the chromosomal determination of the sex of an individual

Deduce the sex of a human individual given a karyogram.

XY = Male
XX = Female

Define genome, gene and allele.

genome - the complete set of genes of an organism.

genes - the individual DNA sequences that encode for specific traits. Alleles are variations of specific genes.

Outline the cause and effect of "single-nucleotide polymorphisms" in genomes.

Polymorphism takes place when more than one allele for a gene exists in a population. Alleles usually differ from one another by just one base pair (single-nucleotide polymorphisms, or SNPs).
These small changes give rise to all the diversity within a species.

Describe reasons why a larger genome does not necessarily indicate presence of more genes.

As with genome size, having more protein-coding genes does not necessarily translate into greater complexity. This is because the eukaryotic genome has evolved other ways to generate biological complexity.

Compare variation in genomes sizes and gene sequences within and between species.​ ​

The number of chromosomes and the order of genes within a chromosome are the same across a species.

The individual nucleotide bases vary within a species.

State the units for measuring genome size.

Genome size can be measured in kilobases (1 kb = 1000 bp), megabases (1 mb = 1000000 bp), or as the mass of DNA in picograms (1 pg = 10-12 g).

Use a database to compare genome sizes to determine if there is a relationship between the number of genes in a species and the species complexity in structure, physiology and/or behavior.

There is no relationship between the number of genes in a species and the complexity of the species - for example, rice has 17,000 more genes than humans, but is not necessarily more advanced.

Define "sequence" in relation to genes and/or genomes.

The sequence of the bases (A, T, C, and G) encodes the biological information that cells use to develop and operate. The sequence of DNA determines the function of genes and other parts of the genome.

State what has sped the DNA sequencing process.

Technological improvements

List applications of genome sequencing.

- Deduce evolutionary origins
- Identify relationships between species and trace the diverging pathways from common ancestors
- Conserve and protect biodiversity
- Personalized medicine
-Help control the spread of infectious diseases

Discuss ethical considerations of genome sequencing.

- circumstances under which research results are disclosed to research participants
- the obligations, if any, owed to participants' close genetic relatives
- options regarding how future uses of samples and data taken for whole-genome sequencing are dealt with.